This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-330230, filed Nov. 19, 1999, the entire contents of which are incorporated herein by reference.
This invention relates to a battery capacity indication circuit and an indication method thereof for use in an electronic device having a battery as a power supply, for example, a cellular communication terminal apparatus such as a cellular telephone or the like, a portable personal computer, a PDA (Personal Digital Assistants), a portable audio player, and a video camera, to detect an output of the battery and provide information relating to the capacity thereof and, more particularly, to a battery-operated electronic device and a cellular communication terminal apparatus comprising the battery capacity indication circuit.
Recently, various cellular communication terminal apparatuses such as cellular telephones, PDA and the like have been used in accordance with the development of the communications technology and the variety of demand on the cellular communication.
Incidentally, the terminal apparatus of this kind has a battery as its power supply. For this reason, the battery needs to be constantly charged or exchanged to the other. Thus a battery capacity indication circuit is generally provided in the cellular communication terminal apparatus. This circuit discriminates the remaining capacity of the battery on the basis of the output voltage thereof and displays it on a display unit. Therefore, the user can confirm the remaining capacity of the battery by this display unit, at any time, during the operation of the terminal apparatus.
However, the conventional battery capacity indication circuit of this kind has the following problem that should be solved. That is, current consumption of the apparatus is temporarily increased when the apparatus becomes in a specific operation state, for example, at the time of outputting a ringing tone accompanying an incoming call, operating a vibrator, turning on a back light of the liquid crystal display, and the like. Thus, the battery output shows the voltage drop. A current apparatus has a battery of small capacity for downsizing and weight reduction. Therefore, the voltage drop of the battery output cannot be neglected.
In the conventional remaining capacity indication circuit, however, the detected value is always displayed as it is without considering the voltage drop of the battery output. For this reason, an erroneous remaining capacity lower than an actual value is displayed in the above-described specific operation state. In this case, it is not preferable that the user may commit an erroneous operation of turning off the power supply of the apparatus by judging that the battery would be exhausted soon, though the apparatus can be still operated.
On the other hand, canceling the detection of the battery voltage not to display the remaining capacity in the above-described specific operation state has been proposed to prevent such inconvenience. According to this manner, however, the user cannot confirm the remaining capacity of the battery during the operations in the specific operation state. For this reason, even if the remaining capacity of the battery is reduced and the battery voltage is lower than a predetermined value such that the power-down suddenly occurs, the user cannot confirm the reason therefor.
This invention is accomplished in consideration of the above-described circumstances. The object of this invention is to provide a battery capacity indication circuit and indication method thereof capable of exactly indicating a battery capacity even if the battery output is temporarily varied in a specific operation state of the electronic circuit, and also provide a battery-operated electronic device and cellular communication terminal apparatus comprising the indication circuit.
To achieve the object, a battery capacity indication circuit according to this invention comprises a function of detecting and keeping an output value of the battery, a function of discriminating whether the electronic circuit is in a first operation state of consuming the power of smaller than a predetermined value or a second operation state of consuming the power of greater than the predetermined value, a function of comparing the output value of the battery detected by the detection function with a predetermined threshold value if it is discriminated by the discrimination function that the electronic circuit is in the second operation state, and a function about the battery capacity. The indication function generates and indicates information about the capacity of the battery on the basis of the output value of the battery detected by the detection function in the first operation state before the electronic circuit becomes in the second operation state, if it is determined by the comparison function that the output value of the battery is equal to or greater than the threshold value.
Therefore, according to this invention, even in a case where a specific operation of consuming comparatively large current, such as outputting a reception ringing, vibrating operation of the vibrator, putting on the display backlight or the like, is executed in the electronic circuit, if the output value of the battery is still very great, the remaining capacity of the battery detected in a standby state immediately before the specific operation or in a communication state is displayed without receiving influence of temporary voltage drop of the battery voltage caused by the specific operation. For this reason, inconvenience of erroneously displaying the remaining capacity of the battery smaller than the actual value can be prevented, and thereby the user can exactly recognize the remaining capacity of the battery.
In addition, the battery capacity indication circuit according to this invention is characterized in that the indication function further comprises a function of generating and indicating information about the capacity of the battery on the basis of a current output value thereof, when it is discriminated as a result of the comparison executed by the comparison means that the output value of the battery is smaller than the threshold value.
Therefore, according to this invention, even in a specific operation state, the user can confirm that the remaining capacity of the battery is being exhausted and can thereby properly judge whether or not he can continue the subsequent operations. In addition, even if the supply of the power is suddenly interrupted during the specific operation, the user can clearly understand the reason.
A plurality of specific examples of the indication function can be conceived as follows.
The first structure is to generate and indicate the information representing the remaining capacity of the battery on the basis of the output value thereof detected by the detection function.
The second structure is to generate and indicate the information representing the power consumption of the battery on the basis of the output value thereof detected by the detection function.
The third structure is to obtain the remaining capacity of the battery on the basis of the output value thereof detected by the detection function, obtain the remaining time to operate the electric circuit from the remaining capacity, and indicate the information representing the remaining time.
The fourth structure is to obtain the remaining capacity of the battery on the basis of the output value thereof detected by the detection function, obtain the remaining number of times to operate the electric circuit from the remaining capacity, and indicate the information representing the remaining number of times.
Further, the information can be displayed by selecting one or more of the first to fourth structures, in accordance with the user""s selecting operation.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.